Synchronizing clocks over simplex circuits having central-battery telephone signaling



H. W. DRAKE SYNCHROHIZING CLOCKS OVER SIMPLEX CIRCUITS HAVING CENTRAL BATTERY TELEPHONE SIGNALING Filed Maruh 19, 1926 movie uz mm Patented Oct. 18, 1927.

UNITED STATES I 1,646,354 PATENT OFFICE.

HERBERT W. DRAKE, OF EAST ORANGE, NEW JERSEY, ASSIGNOR TO THE WESTERN UNION TELEGRAPH COMPANY, OF NEW" YORK, N. Y., A CORPORATION OF NEW YORK.

-SYNCHRONIZING cLocKs o'vnn smrnnx ,cmourrs HAVING CENTRAL-BATTERY TELEPHONE SIGNALING. 2

Application flled ltazgch 19, 1926. Serial No. 95,992.

' This invention relates to synchronizing apparatus for clocks in which a telephone line serves as the medium for the transmis-.

sion of the synchronizing impulse. It is 5 particularly concerned with a means for synchronizing over simplex circuits having central battery signaling whereby the resistance sf the synchronizing circuit is reduced to a minimum.

According to present practice, the simplex circuit of a composite system has a bridge arrangement of very high resistance and inductance, at the electrical center of which the Morse wire is connected. This high re- 15 sistance makes the circuit unsuitable for clock synchronizing service. By my invention I provide a simplex circuit in which a path to ground is. provided, by way of the clocks to be synchronized, through a con- 20 ductor connected to the electrical center of the telephone repeating coil, and the resistance of this circuit is maintained at a low value by,the use of relays having very low resistance.

with its attendant advantages, will be ap parent upon inspection of the accompanying drawing, which shows the new low resistance method applied to a common battery telephone system in which:

L represents the line-conductors extending between the central oflice and a substation, which may be a branch oflice or any subscribers station. The branch oflice telephone equipment' is connected to the line through the usual telephone repeating coil RC. At the central ofiice a repeating coil is interposed between the line and the telephone ack. These line conductors in parallel rovide a simplex circuit which is groun ed at the central ofiice end through a neutral relay NR, and at the branch oifice through the clocks G, to be s nchronized. As will be apparent from the ollowing description, this simplex circuit serves a double function. When a source of current is in-- sorted .into the branch oilice ground connection, he simplex circuit serves to transmit a calling signal to the central oflice. When, howevera source of current is applied to the central ofiice ground connection, the simplexcircuit serves to transmit a synchroniz- The manner of operation of my system,

ing impulse from central ofiice to all the blocks on the synchronizing circuit.

At the branch office t and 1' represent the usual telephone transmitter and receiver, ands any desired form of switch for completing the talking circuit atthe branch office. The transmitting circuit is closed, upon operation of S, through an inductioneoil and therelay R.

At the central oflice, .a neutral or nonpolar rela NR is arranged for front contact opera ion, and its contacts operate to shunt the condenser K which is in series with the coils 1, 2 of the repeatin coil. A direct current circuit is completed by way of this shunt from battery B through both windings of line relay Zr and both armatures and back contacts of cut-0d .relay on The armature of 11" controls the circuit of a calling signalor line signal lamp 1. Cutofi relay cr has its circuit under control of ack J, in the usual manner. The usual superviso signal 8 is provided, normally shunted. t rough operation of the supervisory relay sr, when the operatorslistening key lk is closed, but lighted upon opening of the shunt about the repeating coil condenser K when the relay tilt is deener gized as the branch oflice operator opens switch S tov restore her telephene apparatus to its inoperative condition.

The synchronizing means of my invention comprisesa master control clock MC which.

controls the closing of an energizing circuit through control relay 60R and signal SR:

Operation of these two relays completes a circuit from generator G over armature-and contact of relay-COB, armature and contact of relay SR, conductor- 22, repeater coils R0,

the line conductors Lin parallel, armature and back contact of relay B, through the clocks C, to be synchronized and to ground. When relay SR operates, it opens the circuit of neutral relay NR, and as its armature falls back, the short circuit about the com denser is opened.-

Briefly, the operation ofthe systemmay be summarized as follows: When the operator at the branch ofiice closes her calling ke indicated at S, which may be any suitab e. yp

the

switch, relay R is energized bg transmitter b'atteryb and, through t e quence' of operations previously described, causes the hghting of line signal lamp Z, thereby indicatin to the central operator that the branch ofice is calling. If it should happen that the master control clock MC closes its switch to send out the synchronizing impulse at the same moment that the "branch oflice operator closes her calling key, the energizing circuit of neutral relay NR will be held open at the armature contact of signal relay SR so that the line signal lamp will not immediately light. However, since this condition lasts for only a second, the time necessa to send out the synchronizing impulse, the ighting of the line signal lamp will be delayed only a second. Immediately upon the opening of the mastercontrol clock circuit, neutral relay NB will be energized and the callin signal will be indicated by the lighting 0 lamp Z.

If the synchronizing impulse is sent out by the master clock while the central and branch oflices are engaged in conversation, the neutral relay NR will-be deenergized only for an instant, thus causing only a momentary deenergization of the supervisory relay 81', which will be indicated by a short flash of the supervisory lamp. The interval is so short that the conversation will not be interrupted.

- When the operator at the branch oflice opens her key or switch S, the relay NR 1s deener zed and removes the short circuit about t e condenser K. This deenergizes the. relay er and thus causes the supervisory lamp 8 to light, indicatin tothe central oflice that i the branch 'o co operator is through.

. When the central station operator calls the branch oflice, she" operates her ringing key rk as'usual after inserting the plu p. m the jack J, thereby ringing the bell at t e branch oflice. When the branch oflice operator closes her switch S, the relay NR is" energized, which closes the short circuit about condenser K and causes the lamp 8 to glow. As

central station operator then closes her listening key lie, the relay 87' is energized and.

closes a shunt around the lamp ,9.

Accordingly, it is clear that the operation of the master control clock will have practically no-eflect on the use of the system for telephone purposes, because "its control of the line lasts for only one second. Moreover, the chance that the telephone line will be in use at the synchronizing moment isonly one to many, particularly in systems, where the synchronizing impulseis sent out only once or twice durin each twenty four hours.

Since the re ays used are low resistance relays and the operatin circuit is simplexed over the telephone con uctors in parallel, it

. is apparent that the resistance of the synchronizmg' circuit is maintained at so low a value as to make possible the transmission of a strong current. impulse for synchronizing purposes.

While I have disclosed only a single embodiment of my invention, it is apparent that various changes may, be made .m the details of the system without departing from V the spirit of the invention.

I claim: 1. In a combined telephone and clock synchronizing system, a master control clock and a plurality'of clocks to be synchronized,

a central ofiice and a branch ofiice and telephone line conductors extending therebe- ,tween and terminating at each end in 'repeating coils, means at each oflice for connecting the electrical midpoint of the line winding ofthe repeating coil to ground to provide a simplex circuit over said telephone conductors in parallel, means for. transmitting a synchronizing current from the master clock to the other clocks over said simplex circuit and means for transmitting a calling current from the branch oflice to the central oflice over said simplex circuit.

2. In a combined telephone and clock synchronizing system, a master control clock and a clock to be synchronized, a pair of tion to ground at said branch ofiice, a plu- I rality clocks in said ground connection and means under-control of said relay for in- ".serting a battery into said ground connection.

4. In a combined telephone and clock syni chronizing circuit, a central station, a local station, a pair of telephone line conductors extending therebetween, means for simplexing the telephone conductors to providea clock synchronizing circuit, a call signal at i the central station, and means under control of the local station to operate the call signal over the simplex s nchronizing circuit.

5. In a combine telephone and clock synchronizing system, a pair of telephone conductors, a call signal at the central station and relay means or controlling operation of the signal over a circuit including the telephone conductors, a master control'clock,

and a clock to be synchronized, a synchronizing circuit superposed upon said relay control circuit, and means under-control'o'f the master clock for delayingoperation of said relay means.

6. In a combined telephone and clock syn-' chronizin system, a central oflice and a branch 0 cc and telephone line conductors extending therebetween, a simplex circuit extendin through the telephone conductors in 'par-al el and connected to ground at the central oflice and at the branch oflice, a relay in the ground connection at the central oflice a plurality of clocks to be synchronized in the ground connection at the branch ofiice, and means under control of the branch oflice for inserting a battery into the last mentioned ground connection, whereby the relay at the central office is operated over the simplex circuit including t e plurality of 0100 s. v

7. In a combined telephone and clock s chronizing system, a central 'oflice an a branch'oflice and telephone line conductors extending therebetween, a simplex circuit comprising a connection to the electrical midpoint of a repeating coil at the central ofiice and a similar connection to a re eating coil at the branch ofiice, a signal at, t e central office, means for operating the signal including a relay in said connection at the central ofiice, a plurality of clocks in the connection .at the branch oflice, a master clock, and means under control of the master clocl: for disconnecting said relay and conmeeting a generator to the said connection at the central ofiice.

' 8. In a combined telephone and clock synchronizin system, a central oflice and a branch 0 cc and telephone line conductors extending therebetween, a simplex circuit comprising a connection to the electrical midpoint of one winding OI a repeating coil at t e central ofiice and a similar connection at the branch ofiice, a relay in-t-he connection at the central office, a condenser in series withthe other winding of the repeating coil at the central 'ofiice, means under control of the relay for short circuiting said condenser, a master control clock, a plurality of clocks to besynchronized in the connection at the branch oflice, a control relay and a signal relay at the central oflice in a circuit under control of the master clock, and means under control of the signal and control relays respectively for disconnecting said first- HERBERT W. DRAKE. 

